The HandleCrashedAircraft function in aircraftcmd.cpp in OpenTTD 0.3.6 through 1.3.2 allows remote attackers to cause a denial of service (out-of-bounds read and crash) by crashing an aircraft outside of the map.

OpenTTD before 1.0.1 does not properly validate index values of certain items, which allows remote authenticated users to cause a denial of service (daemon crash) or possibly execute arbitrary code via a crafted in-game command.

OpenTTD before 1.0.1 allows remote attackers to cause a denial of service (file-descriptor exhaustion and daemon crash) by performing incomplete downloads of the map.

OpenTTD before 1.0.1 accepts a company password for authentication in response to a request for the server password, which allows remote authenticated users to bypass intended access restrictions or cause a denial of service (daemon crash) by sending a company password packet.

OpenTTD 0.3.5 through 1.1.4 allows remote attackers to cause a denial of service (game pause) by connecting to the server and not finishing the (1) authorization phase or (2) map download, aka a "slow read" attack.